Automatic abrasive sand delivery machine especially for water-jet cutting machines

ABSTRACT

An automatic loader of abrasive sand into a storage and supply tank (T) of a machine tool that uses the abrasive sand, and in particular of a cutting machine, includes a loading chamber ( 1 ) for loading the abrasive sand arranged above the supply opening of the tank (T) and having a suction inlet, connected through an air suction pipe ( 6 ) to a vacuum pump ( 2 ), and a sand inlet, in a lower position, connected through a sand suction pipe ( 7 ) to a supply container (S) for abrasive sand. A filter (F) is arranged inside the loading chamber ( 1 ), between the suction inlet and the sand inlet, and the loading chamber ( 1 ) is closed below by a butterfly valve ( 9 ) provided with spring element apt to retain the valve in the closed position when there is no sand inside the loading chamber ( 1 ).

FIELD OF THE INVENTION

The present invention relates to an automatic loader of abrasive sand,particularly for water-jet cutting machines.

BACKGROUND ART

Water-jet cutting machines and, more in general, machines that make useof abrasive sand for operation thereof, are usually provided with an ownstorage tank, into which a supply of abrasive sand is loaded. This isthen sent, by pressurised air, into a mini-hopper loading the cuttingmachine from which the abrasive sand is then drawn automatically forcutting, as required.

The storage tank allows the cutting machine to operate for apredetermined period of time and must hence be periodically reloaded, toallow uninterrupted operation of said machine.

In the current state of the art, the loading of this type of cuttingmachine servicing thanks is still performed completely by hand by theoperator in charge of the cutting machine, using supplies of abrasivesand in 25-kg paper bags, packaged in bulk bags containing 40 bags eachand hence weighing around 1 ton.

The bulk bag is positioned by mechanical means as close as possible tothe machine or set of machines and then the operator carries the smallerbags on his shoulder all the way from the 1,000-kg bulk bag to thestorage tank, then cuts open the bag paper pouring the abrasive into thetank and finally dispose of the paper bag in the waste disposal area.

PROBLEM AND SOLUTION

The current manual procedure for loading storage tanks with abrasivesand, apart from obviously being slow and tiresome, also involves a notnegligible cost in terms of even unskilled labour, which must be keptavailable in order to fill the tanks whereas the workers could bedirected more beneficially to more challenging tasks that cannot beautomated.

Furthermore, the use of abrasive sand packaged in relatively lightbags—essential for manual loading to be possible—also causes a notnegligible consumption of resources, both due to the greater cost of theabrasive product supplied in bags in relation to the same productsupplied loose within said bulk bags, and due to the management of thebag paper during the bag opening and disposing steps.

The problem underlying this invention is hence to propose a piece ofapparatus which allows the automatic loading of said storage tanks ofcutting machines, starting from abrasive sand in a loose condition, i.e.not pre-packaged in small bags, thus making it possible to fullyeliminate the manual handling of said bags. This object is achievedthrough an automatic loader having the features defined in Claim 1. Thedependent claims define other preferred features of the apparatus of theinvention.

BRIEF DESCRIPTION OF THE DRAWING

Further features and advantages of the automatic loading apparatus ofthe invention will in any case be more clearly apparent from thefollowing detailed description of a preferred embodiment thereof, givenpurely as a non-limiting example and illustrated in the attacheddrawing, which shows a diagrammatic, partially sectioned front view ofsaid apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As stated above, the automatic loader for abrasive sand of thisinvention is intended for servicing a machine tool which makes use ofsaid abrasive sand in its operating cycle, in particular for water-jetcutting machines. The specific type of such a machine tool is not,however, relevant for the operation of the apparatus of the inventionand hence in the drawing only the storage tank T for abrasive sand isshown, the outlet U of which is connected—in a manner known per se, andin any case irrelevant for the purposes of the present invention—to themachine tool and the opening E of which is, as per the known art, openoutwards for the manual loading of the tank by an operator.

The automatic loading apparatus of the invention comprises in essence aloading chamber 1, positioned above the opening E of the tank T andconnected, on one side, to a vacuum pump 2 and, on the other side, to abulk bag S containing abrasive sand in a loose state. The operation ofthe vacuum pump 2 is controlled through a processing unit housed in anelectrical console 3, according to the operating logic that will bedescribed below. The bulk bag S is arranged inside a sturdy metal frame4 and is fastened on to the top thereof to hooks 4′ projecting from theupper frame crosspiece through retaining ties 5, so as to prevent itfrom collapsing as the abrasive sand contained therein is drawn out.

The chamber 1 is connected to the vacuum pump 2 and to the bulk bag S bymeans of pipes 6 and 7, respectively, preferably made of flexible,abrasion-resistant plastic materials, appropriately reinforced by a wirebraid that prevents them from being collapsed when a degree of vacuum isformed therein, as pump 2 is actuated. The pipe 6 is connected at thetop of the chamber 1, while the pipe 7 is connected to the side of thechamber 1, in a lower position with respect to the inlet of pipe 6, soas to allow a filter F to be housed in the upper portion of the chamber1, to prevent any undesired migration to the vacuum pump 2 of theabrasive sand entering the chamber 1 from the pipe 7. The pipe 7 endswith a steel intake nozzle 8, intended to be inserted into the bulk bagS; by preference this nozzle consists of a double-walled pipe, with aplurality of inlet slots formed in each of its side walls. The innerwall of the nozzle 8 is then connected to the pipe 7, while the outerwall of the nozzle 8 forms a protection gap for the inner wall, thusallowing the sand to be sucked into the pipe 7 from a number of entrypoints—above, below and laterally to the nozzle 8—and hence preventingany possible problem of said nozzle being occluded by the walls of thebulk bag S.

Finally, the chamber 1 is closed off at the bottom by a butterfly valve9 that is normally kept in the closed position by retaining spring meanshaving a low loading force, so as to open easily under the weight of thesand when the chamber 1 is even only partly loaded. The butterfly valve9 is also provided with a control micro-switch 10 apt to notify thecontrol unit housed in the electrical console 3 of the open or closedposition of said valve.

The operation of the automatic loader of abrasive sand illustrated aboveis extremely easy and effective and will now be briefly disclosed below.

After having positioned the fixed parts of the apparatus in theconfiguration described above and having loaded a bulk bag S full ofabrasive sand into the frame 4, fastening the ties 5 thereof to thecorresponding hooks 4′, the bulk bag S is opened and the nozzle 8connected to the pipe 7 is inserted into the same. In the drawing thenozzle is shown as fully inserted inside the abrasive sand contained inthe bulk bag, but in actual fact it is enough just to insert in theabrasive sand the tip of the nozzle 8, since said tip will penetrateinto the bulk bag S due to the suction effect caused by the vacuum pump2, quickly positioning itself with its lower end at the bottom of saidbulk bag.

Before starting up the vacuum pump 2, the control unit housed in theelectrical console 3 is set on the values of the specific plant, byadjusting the continued operating time of the vacuum pump, defined aswork cycle, based on the internal volume of the chamber 1 and on thesuction flow rate of the sand. In other words, the duration of the workcycle is set so as to cause just a partial filling of the chamber 1 inall the various possible working and environmental conditions(temperature, humidity, type of sand etc.).

At the beginning of any work cycle of the vacuum pump 2, a vacuum isfirst produced inside the chamber 1, and then inside pipe 7 and nozzle8, which result in drawing in a mixture of air and sand from the bulkbag S. The air entering the loading chamber 1 passes through the filterF and is expelled by the pump 2, while the sand dragged in by the sameaccumulates on the bottom of the chamber 1. The vacuum maintained in thechamber 1 prevents the butterfly valve 9 from opening even when theweight of abrasive sand acting thereon becomes greater than the loadingforce of the retaining spring means of said valve. At the end of eachwork cycle the vacuum pump 2 stops, the butterfly valve opens under theweight of the sand and the sand thus falls by gravity into the tank T.When the chamber 1 has been emptied, the retaining spring means of thebutterfly valve 9, no longer contrasted by the weight of the overlyingsand, bring the valve 9 back into a closed position and the micro-switch10 gives the consent to the control unit to automatically start a secondwork cycle for filling chamber 1. When initially setting the controlunit, it is therefore also necessary to set on also the number ofsuccessive work cycles that the vacuum pump 2 must perform beforestopping and requiring reactivation by the operator. Depending on theoperator's requirements and preferences, this number of work cycles canbe set as follows:

-   -   a—to a finite number of work cycles, for example proportional to        the size of the storage tank T of the machine tool or to the        consumption of abrasive required per production batch, so that        the vacuum pump 2 will stop after filling the tank T completely        or, respectively, after loading the amount of abrasive material        necessary for one production batch;    -   b—to an infinite number of work cycles, so that the vacuum pump        2 is switched on automatically each time the butterfly valve 9        is in the closed position. In this case, when the tank T is        full, there is no room in the tank T for the sand coming out of        the chamber 1 and the sand accumulates therefore in the lower        area of the chamber 1, below the butterfly valve 9, which hence        remains blocked in the open position, preventing the vacuum pump        2 from starting up again. When the drawing by the machine tool        has consumed enough of the sand in the tank T to release the        butterfly valve 9, the latter returns to the closed position and        allows another work cycle to start.

Obviously, therefore, in the first operating mode the tank T is filledand then emptied alternately, while in the second case it always remainsconstantly full. Either operating mode can be selected at will by theuser, depending on the specific work requirements.

It should be clear from the above description that the apparatus of thepresent invention has fully achieved the object set above, making itpossible to fully remove the burdensome and tiresome manual loading ofabrasive sand, to the benefit of the smooth operation of the cuttingmachines to which the storage tank T is attached, and to the cleannessof the premises, the complete elimination of paper bags to be disposedof and, finally, the lower cost of the abrasive material used when, asstated, this is supplied loose in bulk bags.

It is in any case intended that the apparatus of the invention shouldnot be considered to be limited to the particular arrangementillustrated above, which represents only an exemplifying embodimentthereof, but that a number of variants are possible, all within theability of a person skilled in the art, without departing from the scopeof said invention, as defined by the following claims.

1) Automatic loader of abrasive sand into a storage and supply tank (T)of a machine tool using said abrasive sand, and in particular of acutting machine, characterised in that it comprises a loading chamber(1) of the abrasive sand arranged above the supply opening of said tank(T) and having a suction inlet, connected through an air suction pipe(6) to a vacuum pump (2), and a sand inlet, in a lower position,connected through a sand suction pipe (7) to a container (S) for thesupply of abrasive sand, a filter (F) being arranged inside the loadingchamber (1) between said suction inlet and said sand inlet, and in thatsaid loading chamber (1) is closed off at the bottom by a butterflyvalve (9) provided with spring means apt to retain said valve in theclosed position when there is no sand inside said loading chamber (1).2) Automatic loader of abrasive sand as claimed in claim 1, wherein theoperation of said vacuum pump (2) is controlled by a control unit (3)which actuates said pump for a predetermined adjustable number ofsubsequent work cycles, the duration of each work cycle being predefinedso that the activation of the vacuum pump (2) for an entire work cyclecauses just the partial filling of said loading chamber (1). 3)Automatic loader of abrasive sand as in claim 2, wherein said butterflyvalve (9) further comprises a micro-switch (10) connected to saidcontrol unit (3) apt to indicate whether said butterfly valve is open orclosed, and wherein the operation of the pump (2) is switched off whensaid butterfly valve is in the open position. 4) Automatic loader ofabrasive sand as in claim 1, wherein said supply container consists of anon-rigid bulk bag (S) full of abrasive sand hooked, by integral ties(5) positioned at its top, to corresponding hooks (4′) formed in theupper part of a sturdy, metal support frame (4). 5) Automatic loader ofabrasive sand as in claim 4, wherein said sand suction pipe (7), at thesupply container (S) side, is provided with an end intake nozzle (8),consisting of a double-walled metal pipe provided with a plurality ofinlet slots formed in its side walls. 6) Automatic loader of sand as inclaim 5, wherein the inner wall of the intake nozzle (8) is connected tothe sand suction pipe (7), while the outer wall of the intake nozzle (8)causes the formation of a protection gap to prevent the intake nozzlefrom becoming blocked by the walls of the bulk bag (S). 7) Automaticloader of sand as in claim 1, wherein said air suction pipe (6) and sandsuction pipe (7) are flexible pipes made of abrasion-resistant, plasticmaterial, reinforced with metallic materials in order to prevent themfrom being crushed. 8) Automatic loader of sand as in claim 1, whereinsaid number of work cycles pre-set in the control unit is a finitenumber calculated in proportion to the size of the storage tank (T)and/or to the anticipated consumption of abrasive in respect of oneproduction batch. 9) Automatic loader of sand as in claim 1, whereinsaid number of work cycles pre-set in the control unit is an infinitenumber and the operation of the vacuum pump (2) is interrupted only whenthe micro-switch (10) indicates that the butterfly valve (9) is open,i.e. when the abrasive sand of a work cycle leaving the loading chamber(1) is fully housed in the underlying storage tank (T).